Some elevator door operating systems consist of a reversible motor, a belt, a speed reducing pulley, a transmission pulley, an idler pulley, and a continuous toothed belt. The motor transmits torque via the belt to the speed reducing pulley. The speed reducing pulley is attached to the transmission pulley. The cog belt, which extends around the transmission and idler pulleys, is driven by the transmission pulley. A portion of the cog belt travels linearly between the transmission pulley and the idler pulley. The linear motion of the cog belt is transmitted to each car door panel by means of a linkage.